In a multiple-input multiple-output (MIMO) technology, not only a spatial multiplexing gain provided by a MIMO channel can be used to increase a channel capacity, but also a spatial diversity gain provided by the MIMO channel can be used to improve channel reliability and decrease a bit error rate. Therefore, a MIMO system gradually becomes a research focus in the field of communications.
In a time division duplex (TDD) system, by using a beamforming (BF) technology, reciprocity between an uplink channel and a downlink channel can be used to weight a transmitted beam, so as to generate a directional beam and target the beam at target user equipment (UE).